The fellow to the right is, of course, Yeenoghu, demon prince of gnolls and lord of ghouls, as illustrated by David C. Sutherland III in the AD&D Monster Manual. I used to find the illustration rather creepy as a younger man. There's something mildly unnerving about the stiffness of its pose that, far from a source of derision for me, as it is for many who don't like Sutherland's work, actually heightened its effectiveness. Yeenoghu does look mildly goofy, but in a way that reminds me he's not just another monster but something wholly "unnatural."
In any case, I once heard a story about the creation of Yeenoghu by Gary Gygax. The story goes that players in the Greyhawk campaign, having run afoul of one too many demon lords and archdevils whom they accidentally summoned by speaking their names aloud, got into the practice of using circumlocutions to avoid repeating past mistakes. One such circumlocution was "You-Know-Who." After a while of doing this, Gary sprang Yeenoghu on his players, on the assumption that his name sounded enough like the phrase that he might answer by traveling to the Prime Material Plane.
I always thought the story sounded plausible, since Gary loved puns and wordplay and was never one to give a sucker an even break. Eventually, I remembered the story and asked Gary about him and he told me it had no basis in fact, but was merely an urban legend. A pity, I thought.
(More posts later as time permits. Been busy the last couple of days and will likely be so for a little while longer)